Separation of zirconium and hafnium fluorides by the sublimation–sorption method

A preparation method of zirconium tetrafluoride (ZTF) of the nuclear degree of purity for one separation stage is proposed and confirmed experimentally. For this purpose, initial ZTF vapors should be passed inside the powderlike zirconium dioxide layer 140–150 mm in height or above its layer 1000–1100 mm in length. A process cascade for the fabrication of nuclear-pure ZTF and HTF with the hafnium content higher than 99% for one separation stage in the absence of process wastes is developed and calculated. It is shown that the proposed process cascade for the separation and concentration of ZTF and HTF for one stage makes it possible to prepare ZTF with a hafnium content up to 0.01 wt % from the initial ZTF with a hafnium concentration of 2.0 wt % and a hafnium concentrate with a hafnium content higher than 99%.     

Phase modulation of mid-infrared radiation in double-quantum-well structures under a lateral electric field

The modulation of polarized radiation by GaAs/AlGaAs structures with tunnel-coupled double quantum wells in a strong lateral electric field is studied. The spectra of the variation in the refractive index under a lateral electric field in the vicinity of the intersubband resonance are experimentally investigated.     

Carrier heating in quantum wells under optical and current injection of electron-hole pairs

Carrier heating in GaAs/AlGaAs quantum wells (QWs) under optical interband pumping in the spontaneous-emission mode has been studied. The electron temperature was determined as a function of the pumping intensity. The effect of the electric field on the photoluminescence spectrum was examined. The change in the carrier concentration with the drive current in the spontaneous- and stimulated-emission modes in InGaAsSb/InAlGaAsSb QWs was determined from electroluminescence spectra. The rise in the temperature of hot carriers, which results in the increase in the carrier concentration with the drive current, was roughly estimated.     

Spontaneous Emission and Lasing of a Two-Wavelength Quantum-Cascade Laser

Semiconductors - The results of experiments on the fabrication (by molecular-beam epitaxy) and investigation of the heterostructures of a two-frequency quantum-cascade laser produced on the basis...     

Photoinduced and equilibrium optical absorption in Ge/Si quantum dots

The results of studies of the optical absorption spectra in Ge/Si quantum dot structures in the mid-infrared region are reported. Two types of structures different in terms of the method used for quantum dot formation and in terms of barrier layer thickness are explored. The photoinduced absorption associated with the nonequilibrium population of hole states and optical absorption in structures doped to different levels are investigated. Specific features that are associated with occupation of the ground and excited states of quantum dots and exhibit a polarization dependence are observed. From the experimental data, the energy spectrum of holes is determined for structures of both types.